In a magnetic tape recording/reproducing apparatus, especially of a type wherein a two-reel tape pack is used, it is required to feed the tape pack loaded in the apparatus into a recording/reproducing position and to advance or retire a head plate on which a head and pinch rollers are mounted, and it is also required to temporarily stop a play-operation mode or to replace the tape pack loaded in the apparatus by a new one and to effect a fast forward-operation and a rewind-operation. Known mechanisms for carrying out these operations are generally based on either one of two approaches. One approach is based on an attempt to carry out the operations with a reduced number of operation levers, while the other idea is to provide operation levers for the respective operations and to make the operation levers carry out the operations, respectively. These known mechanisms of either type, however, have defects and disadvantages. More particularly, though the former mechanism has such an advantage that the operation portion of a recording/reproducing apparatus is simplified, it has a shortcoming of relatively poor operability because the number of the mechanism components to be actuated by each of the operation levers are increased and the work stroke is also increased. On the other hand, the latter mechanism can solve this problem but it is not possible to make uniform the forces and work strokes required for the respective operations. Through a play-stop mode can be established by retiring a head plate alone in an ejecting operation, when it is required to change tape transport modes from one mode to another, the operation in said mode must be once stopped to allow the operation in said another mode. In addition, where the apparatus is of a pushbutton type, when a number of push buttons are arranged in an array there is a possibility of inadvertent double depression of the push buttons which can damage or deform the mechanism.